Plasma processing method

ABSTRACT

A plasma processing method for a workpiece in a plasma processing apparatus includes (i) performing a first plasma processing on a workpiece, and (ii) performing a second plasma processing on the workpiece. Power of second radio frequency waves set in the second plasma processing is greater than the power of the second radio frequency waves set in the first plasma processing. In the second plasma processing, a magnetic field distribution having a horizontal component on an edge side of the workpiece greater than a horizontal component on a center of the workpiece is formed by an electromagnet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese PatentApplication No. 2017-185082, filed on Sep. 26, 2017, with the JapanPatent Office, the disclosure of which is incorporated herein in itsentirety by reference.

TECHNICAL FIELD

Exemplary embodiments of the present disclosure relate to a plasmaprocessing method and a plasma processing apparatus.

BACKGROUND

In the manufacture of an electronic device, a plasma processing methodis executed using a plasma processing apparatus to process a workpiece.The plasma processing apparatus generally includes a chamber body, a gassupply unit, a stage, a first radio frequency power supply, and a secondradio frequency power supply. The gas supply unit is configured tosupply a gas to the inner space of the chamber body. The stage isprovided in the inner space of the chamber body and is configured tosupport a workpiece placed thereon. The workpiece is placed on the stagesuch that the center thereof is located on a central axis of the chamberbody. The stage includes a lower electrode. The first radio frequencypower supply is configured to generate first radio frequency waves forgenerating plasma. The second radio frequency power supply is configuredto generate second radio frequency waves. A frequency of the secondradio frequency waves is lower than a frequency of the first radiofrequency waves. The second radio frequency waves are supplied to thelower electrode. In the plasma processing method using the plasmaprocessing apparatus, the gas is excited in the inner space by the firstradio frequency waves, so that plasma is generated. In addition, thesecond radio frequency waves are supplied to the lower electrode. Thus,ions in the plasma are accelerated toward the workpiece, and theworkpiece is irradiated with the accelerated ions.

As a type of plasma processing method, there is a plasma processingmethod in which two plasma processings are sequentially applied to aworkpiece. Such a plasma processing method is described in JapanesePatent Laid-Open Publication No. 2015-173240. The plasma processingmethod disclosed in Japanese Patent Laid-Open Publication No.2015-173240 is executed to selectively etch a first region formed ofsilicon oxide with respect to a second region formed of silicon nitride.In the plasma processing method, a processing using plasma of afluorocarbon gas and a processing using plasma of a rare gas areexecuted. In the processing using the plasma of the fluorocarbon gas, adeposit film containing fluorocarbon is formed on the workpiece. Whilethe processing using the plasma of the fluorocarbon gas is executed,power of the second radio frequency waves is set to relatively low power(e.g., 0 watts). In the plasma processing using the rare gas, theworkpiece is irradiated with ions of the rare gas. While the plasmaprocessing using the rare gas is executed, the second region isprotected by the deposit film, and the first region is etched byradicals of the fluorocarbon in the deposit film. While the plasmaprocessing using the rare gas is executed, power of the second radiofrequency waves is set to relatively high power. The plasma processingmethod is used to form an opening in a self-aligned manner by etchingthe first region provided in a recess provided by the second region.

SUMMARY

In an aspect, a plasma processing method for a workpiece in a plasmaprocessing apparatus is provided. The plasma processing apparatusincludes a chamber body, a stage, a lower electrode, a gas supply unit,a first radio frequency power supply, a second radio frequency powersupply, and an electromagnet. The stage provides a placing region for aworkpiece, and is provided in an inner space. The center of the placingregion is located on a central axis of the chamber body. The lowerelectrode is provided in the stage. The gas supply unit is configured tosupply a first gas and a second gas to the inner space of the chamberbody. The first radio frequency power supply is configured to supplyfirst radio frequency waves. The second radio frequency power supply isconfigured to supply second radio frequency waves and is electricallyconnected to the lower electrode. A frequency of the second radiofrequency waves is lower than a frequency of the first radio frequencywaves. The electromagnet is configured to form a magnetic field in theinner space of the chamber body.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a plasma processing method accordingto an embodiment.

FIG. 2 is a view schematically illustrating an embodiment of a plasmaprocessing apparatus that may be used to execute the plasma processingmethod illustrated in FIG. 1.

FIG. 3 is a graph illustrating a calculation result of an electric fieldintensity distribution in an inner space of a chamber body.

FIG. 4 is a plan view illustrating an internal configuration of agrounded conductor of the plasma processing apparatus illustrated inFIG. 2.

FIG. 5 is a view illustrating a calculation result of a magnetic fielddistribution that may be formed by the plasma processing apparatusillustrated in FIG. 2.

FIG. 6 is a graph illustrating a measurement result of an ion fluxdistribution in the inner space of the plasma processing apparatusillustrated in FIG. 2.

FIG. 7 is a partially enlarged cross-sectional view of an exemplaryworkpiece to which an embodiment of the method illustrated in FIG. 1 isapplicable.

FIG. 8 is a partially enlarged cross-sectional view of the workpieceprocessed from a state illustrated in FIG. 7.

FIG. 9A is a partially enlarged cross-sectional view of the workpiece ina state after execution of step ST1 in an embodiment of the methodillustrated in FIG. 1, and FIG. 9B is a partially enlargedcross-sectional view of the workpiece in a state after execution of stepST2 in the embodiment of the method illustrated in FIG. 1.

FIG. 10 is a partially enlarged cross-sectional view of the workpieceafter the embodiment of the method illustrated in FIG. 1 is applied.

DESCRIPTION OF EMBODIMENT

In the following detailed description, reference is made to theaccompanying drawing, which form a part hereof. The illustrativeembodiments described in the detailed description, drawing, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

With the miniaturization of an electronic device, the width of theabove-described recess is small. When a deposit is thickly formed on thefirst region that is present in the narrow recess, the etching of thefirst region is not performed by the plasma processing using the raregas. Thus, it is necessary to reduce the film thickness of the depositfilm formed on the workpiece. When the film thickness of the depositfilm is small, in order to prevent the etching of the second region, itis necessary to lower the energy of the ions of the rare gas with whichthe workpiece is irradiated. In order to lower the energy of the ions,it is conceivable to use the second radio frequency waves having a radiofrequency. When the frequency of the second radio frequency waves ishigh, an electric field intensity distribution having a high electricfield intensity on the center of the workpiece and a low electric fieldintensity on the edge side of the workpiece is formed. That is, anon-uniform electric field intensity distribution is formed in the innerspace such that the electric field intensity decreases as the distancefrom the central axis in a radiation direction increases. As a result, anon-uniform plasma density distribution is formed in the radiationdirection with respect to the central axis. Such a plasma densitydistribution gives rise to non-uniformity of a plasma processing in aradial direction. Thus, it is required to make a uniform plasma densitydistribution in the plasma processing using the rare gas. In addition,in an arbitrary plasma processing method including a first plasmaprocessing in which the power of the second radio frequency waves (biasradio frequency waves) is set to low power and a second plasmaprocessing in which power of the second radio frequency waves is set tohigh power, it is also required to make a uniform plasma densitydistribution during execution of the second plasma processing.

In an aspect, a plasma processing method for a workpiece in a plasmaprocessing apparatus is provided. The plasma processing apparatusincludes a chamber body, a stage, a lower electrode, a gas supply unit,a first radio frequency power supply, a second radio frequency powersupply, and an electromagnet. The stage provides a placing region for aworkpiece, and is provided in an inner space. The center of the placingregion is located on a central axis of the chamber body. The lowerelectrode is provided in the stage. The gas supply unit is configured tosupply a first gas and a second gas to the inner space of the chamberbody. The first radio frequency power supply is configured to supplyfirst radio frequency waves. The second radio frequency power supply isconfigured to supply second radio frequency waves and is electricallyconnected to the lower electrode. A frequency of the second radiofrequency waves is lower than a frequency of the first radio frequencywaves. The electromagnet is configured to form a magnetic field in theinner space of the chamber body.

A plasma processing method according to an aspect is executed in a statewhere a workpiece is accommodated in an inner space of a chamber body.The plasma processing method includes (i) performing a first plasmaprocessing on the workpiece by plasma generated from a first gassupplied to the inner space, and (ii) performing a second plasmaprocessing on the workpiece by plasma generated from a second gassupplied to the inner space. Power of the second radio frequency wavesset in the second plasma processing is greater than power of the secondradio frequency waves set in the first plasma processing. In the secondplasma processing, a magnetic field distribution having a horizontalcomponent on an edge side of the workpiece that is greater than ahorizontal component on a center of the workpiece is formed by theelectromagnet.

In the plasma processing method according to the aspect, while thesecond plasma processing is executed, an electric field intensityincreases on the center of the workpiece, and the electric fieldintensity decreases on the edge side of the workpiece. That is, whilethe second plasma processing is executed, a non-uniform electric fieldintensity distribution is formed in a radiation direction with respectto a central axis. In addition, while the second plasma processing isexecuted, the above-described magnetic field distribution is formed inthe inner space. In a portion in which the magnetic field having thegreater horizontal component is formed, the stay time of electronsincreases. As a result, the density of plasma increases in the portionin which the magnetic field having the greater horizontal component isformed. Therefore, a plasma density distribution becomes uniform duringexecution of the second plasma processing. Moreover, since the plasmadensity distribution becomes uniform by the magnetic field distributionformed by the electromagnet, the plasma density distribution may becomeuniform at a high speed at a point in time at which a plasma processingto be executed is switched from the first plasma processing to thesecond plasma processing.

In an embodiment, the executing the first plasma processing and theexecuting the second plasma processing are alternately repeated. Evenwhen the first plasma processing and the second plasma processing arealternately repeated, the plasma density distribution may become uniformat a high speed at a point in time at which a plasma processing to beexecuted is switched from the first plasma processing to the secondplasma processing.

In an embodiment, the workpiece includes a first region formed ofsilicon oxide and a second region formed of silicon nitride. The firstgas includes a fluorocarbon gas. In the first plasma processing, adeposit film containing fluorocarbon is formed on the workpiece. Thesecond gas includes a rare gas. In the second plasma processing, theworkpiece having the deposit film formed thereon is irradiated with ionsof the rare gas to etch the first region. In the embodiment, since thesecond region is protected by the deposit film and the first region isetched, the first region is selectively etched with respect to thesecond region.

In an embodiment, a recess provided by the second region includes thefirst region. In the embodiment, the first region provided in the recessof the second region is etched, so that an opening is formed in aself-aligned manner.

In an embodiment, the frequency of the second radio frequency waves isgreater than 13.56 MHz. In an embodiment, the frequency of the secondradio frequency waves is equal to or greater than 40 MHz. In anembodiment, the frequency of the second radio frequency waves is equalto or greater than 60 MHz.

As described above, in a plasma processing method including a firstplasma processing and a second plasma processing, a plasma densitydistribution may become uniform during execution of the second plasmaprocessing in which power of bias radio frequency waves is set torelatively high power.

Hereinafter, various embodiments will be described in detail withreference to the accompanying drawings. In addition, in the respectivedrawings, the same reference numerals will be attached to the same orcorresponding parts.

FIG. 1 is a flowchart illustrating a plasma processing method accordingto an embodiment. The plasma processing method (hereinafter referred toas “method MT”) illustrated in FIG. 1 is executed in a state where aworkpiece is accommodated in an inner space of a chamber body of aplasma processing apparatus.

FIG. 2 is a view schematically illustrating an embodiment of a plasmaprocessing apparatus that may be used to execute the plasma processingmethod illustrated in FIG. 1. In FIG. 2, the plasma processing apparatus10 of the embodiment is illustrated as being partially broken in avertically extending plane. The plasma processing apparatus 10illustrated in FIG. 2 includes a chamber body 12. The chamber body 12has a cylindrical shape, and includes a sidewall 12 a and a bottomportion 12 b. The chamber body 12 provides an inner space 12 s. Acentral axis AX illustrated in FIG. 2 is a central axis of the chamberbody 12 and the inner space 12 s. The chamber body 12 is formed of ametal such as, for example, aluminum. The inner wall surface of thechamber body 12 is formed with a film having plasma resistance. Thisfilm may be a ceramic film such as an alumite film or a yttrium oxidefilm. The chamber body 12 is grounded.

The sidewall 12 a is formed with a passage 12 p. The workpiece W passesthrough the passage 12 p when transferred between the inner space 12 sand the outside of the chamber body 12. The workpiece W may have a diskshape like a wafer. The passage 12 p may be opened and closed by a gatevalve 12 g. The gate valve 12 g is provided along the sidewall 12 a.

A stage 14 is provided in the inner space 12 s. The stage 14 issupported by a support member 15. The support member 15 has acylindrical shape and extends upward from the bottom portion 12 b of thechamber body 12. The support member 15 has insulation, and is formed ofa ceramic, for example.

The stage 14 is configured to support the workpiece W. The stage 14shares the central axis AX with the chamber body 12. The stage 14provides a placing region 14 r. The center of the placing region 14 r islocated on the central axis AX. The workpiece W is placed on the placingregion 14 r so that the center thereof is located on the central axisAX.

The stage 14 includes an electrode plate 16, a lower electrode 18, andan electrostatic chuck 20. The electrode plate 16 has a substantiallydisk shape. The electrode plate 16 has conductivity. The electrode plate16 is formed of a metal such as aluminum. The lower electrode 18 has adisk shape. The lower electrode 18 has conductivity. The lower electrode18 is formed of a metal such as aluminum. The lower electrode 18 ismounted on the electrode plate 16. The lower electrode 18 iselectrically connected to the electrode plate 16.

A flow path 18 p is formed in the lower electrode 18. The flow path 18 pextends, for example, in a spiral shape in the lower electrode 18. Aheat exchange medium (e.g., a coolant) is supplied to the flow path 18 pfrom a circulation device 22 (e.g., a chiller unit) for the heatexchange medium. The circulation device 22 is provided outside thechamber body 12. The heat exchange medium supplied to the flow path 18 preturns to the circulation device 22. By heat exchange between the heatexchange medium and the lower electrode 18, the temperature of theworkpiece W placed on the stage 14 is controlled.

The electrostatic chuck 20 is provided on the lower electrode 18. Theelectrostatic chuck 20 has a substantially disk shape. The electrostaticchuck 20 includes a film-shaped electrode in a ceramic body. A DC powersupply 24 is connected to the electrode of the electrostatic chuck 20via a switch. The electrostatic chuck 20 provides the placing region 14r described above. When a DC voltage is applied from the DC power supply24 to the electrode of the electrostatic chuck 20 in a state where theworkpiece W is placed on the electrostatic chuck 20 (on the placingregion 14 r), an electrostatic attractive force is generated between theworkpiece W and the electrostatic chuck 20. The workpiece W is attractedto the electrostatic chuck 20 and held by the electrostatic chuck 20 bythe generated electrostatic attractive force. The plasma processingapparatus 10 may be provided with a heat transfer gas supply line thatsupplies a heat transfer gas (e.g., He gas) to a gap between theelectrostatic chuck 20 and the lower surface of the workpiece W.

One or more heaters (e.g., one or more resistance heating elements) maybe provided inside the electrostatic chuck 20. When power is suppliedfrom a heater controller to the one or more heaters, the one or moreheaters generate heat, so that the temperature of the electrostaticchuck 20, and consequently, the temperature of the workpiece W areadjusted.

In the inner space 12 s of the chamber body 12, a focus ring FR isdisposed so as to surround the edges of the electrostatic chuck 20 andthe workpiece W. The focus ring FR is an annular plate and is formed ofa silicon containing material such as silicon or quartz. The focus ringFR is used to obtain uniformity of a plasma processing.

A cylindrical conductor 26 is provided around the support member 15. Theconductor 26 is grounded. A cylindrical insulator 28 is provided abovethe conductor 26 so as to surround the stage 14. The insulator 28 isformed of a ceramic such as quartz. An exhaust path is formed betweenthe stage 14 and the sidewall 12 a of the chamber body 12. A baffleplate 30 is provided in the exhaust path. The baffle plate 30 is anannular plate. The baffle plate 30 is formed with a large number ofholes in a plate thickness direction thereof. The baffle plate 30 isconfigured by forming a plasma resistant film such as an yttrium oxidefilm on the surface of a base material formed of a metal such asaluminum.

An exhaust pipe 32 is connected to the bottom portion 12 b of thechamber body 12 under the baffle plate 30. The exhaust pipe 32 maycommunicate with the exhaust path. An exhaust device 34 is connected tothe exhaust pipe 32. The exhaust device 34 includes an automaticpressure control valve and a pressure reduction pump such as a turbomolecular pump. When the exhaust device 34 is operated, the pressure inthe inner space 12 s is set to a designated pressure.

An upper electrode 36 is provided above the stage 14. A portion of theinner space 12 s is interposed between the upper electrode 36 and thestage 14. The upper electrode 36 is provided so as to close an upperopening in the chamber body 12. A member 37 is interposed between theupper electrode 36 and the upper end portion of the chamber body 12. Themember 37 is formed of an insulation material. The member 37 may beformed of a ceramic, for example, quartz. In addition, in an embodiment,the member 37 and a portion of the grounded conductor to be describedlater may be interposed between the upper electrode 36 and an upper endportion of the chamber body 12.

In an embodiment, the upper electrode 36 constitutes a showerhead. In anembodiment, the upper electrode 36 includes an upper plate 38 and asupport member 40. The upper plate 38 is formed of, for example,silicon. Alternatively, the upper plate 38 is configured by providing acoating formed of a ceramic such as yttrium oxide on the surface of abase material formed of aluminum. The upper plate 38 is formed with aplurality of gas discharge holes 38 h in a plate thickness directionthereof.

The support member 40 is provided on the upper plate 38. The supportmember 40 is configured to detachably support the upper plate 38. Thesupport member 40 is formed of a conductive material such as aluminum. Agas diffusion chamber 40 d is formed inside the support body 40. Aplurality of holes 40 h are formed in the support member 40 so as toextend downward from the gas diffusion chamber 40 d. The holes 40 h arerespectively in communication with the gas discharge holes 38 h.

A gas supply unit 41 is connected to the gas diffusion chamber 40 d. Thegas supply unit 41 is configured to supply a gas to the inner space 12s. In an embodiment, the gas supply unit 41 is configured to be able tooutput a first gas and a second gas. The first gas and the second gaswill be described later. In addition, the gas supply unit 41 includesone or more flow rate controllers and one or more valves, and isconfigured to individually adjust the flow rates of one or more gases tobe output. The gas output from the gas supply unit 41 is discharged intothe inner space 12 s from the plurality of gas discharge holes 38 hthrough the gas diffusion chamber 40 d and the plurality of holes 40 h.

A flow path 40 p is formed in the support member 40. A chiller unit 42is connected to the flow path 40 p. A coolant such as cooling water iscirculated between the flow path 40 p and the chiller unit 42. Thetemperature of the upper electrode 36 is adjusted by heat exchangebetween the upper electrode 36 and the coolant supplied from the chillerunit 42 to the flow path 40 p.

The plasma processing apparatus 10 further includes a first radiofrequency power supply 43 and a second radio frequency power supply 44.The first radio frequency power supply 43 and the second radio frequencypower supply 44 are provided outside the chamber body 12. The firstradio frequency power supply 43 is configured to mainly generate firstradio frequency waves for generating plasma. The first radio frequencywaves may have a frequency such as, for example 100 MHz, but is notlimited thereto. The first radio frequency power supply 43 iselectrically connected to the upper electrode 36 via a matcher 45 and apower supply conductor 48. The matcher 45 includes a matching circuitfor matching the output impedance of the first radio frequency powersupply 43 with the impedance of a load side (the upper electrode 36side). The power supply conductor 48 is connected at the lower endthereof to the upper electrode 36. The power supply conductor 48 extendsupward from the upper electrode 36. The power supply conductor 48 is acylindrical or rod-shaped conductor, and the central axis of the powersupply conductor 48 substantially coincides with the central axis AX.

The second radio frequency power supply 44 is configured to mainlygenerate second radio frequency waves, that is, bias radio frequencywaves, for introducing ions into the workpiece W. A frequency of thesecond radio frequency waves is lower than a frequency of the firstradio frequency waves. In an embodiment, the frequency of the secondradio frequency waves is greater than 13.56 MHz. In an embodiment, thefrequency of the second radio frequency waves may be equal to or greaterthan 40 MHz. In an embodiment, the frequency of the second radiofrequency waves may be equal to or greater than 60 MHz. The second radiofrequency power supply 44 is electrically connected to the lowerelectrode 18 via a matcher 46. The matcher 46 includes a matchingcircuit for matching the output impedance of the second radio frequencypower supply 44 with the impedance of a load side (the lower electrode18 side).

The plasma processing apparatus 10 further includes a grounded conductor50. The grounded conductor 50 has conductivity. The grounded conductor50 is formed of a metal such as aluminum. The grounded conductor 50 isgrounded. The grounded conductor 50 extends so as to cover the upperelectrode 36 above the chamber body 12. The power supply conductor 48extends upward to the outside of the grounded conductor 50 through thespace surrounded by the grounded conductor 50, and is connected to thefirst radio frequency power supply 43 via the matcher 45 outside thegrounded conductor 50.

In the inner space 12 s of the chamber body 12 of the plasma processingapparatus 10, an electric field intensity distribution having a highelectric field intensity on the center of the workpiece W and a lowelectric field intensity on the edge side of the workpiece W may beformed. That is, a non-uniform electric field intensity distribution inwhich the electric field intensity decreases as the distance from thecentral axis AX increases in a radiation direction (i.e., a radialdirection) may be formed in the inner space 12 s. FIG. 3 is a graphillustrating a calculation result of the electric field intensitydistribution in the inner space of the chamber body. In FIG. 3, thehorizontal axis indicates the distance from the central axis AX in theradiation direction, and the vertical axis indicates the normalizedelectric field intensity. FIG. 3 illustrates a distribution of thenormalized electric field intensity in a case using each of a pluralityof frequencies f2 of the second radio frequency waves. As illustrated inFIG. 3, the non-uniformity of the electric field intensity in theradiation direction becomes conspicuous as the frequency f2 of thesecond radio frequency waves increases. In addition, when the frequencyf2 of the second radio frequency waves is set to a radio frequency, theenergy of ions with which the workpiece W is irradiated decreases.

Under the above-described non-uniform electric field intensitydistribution, the plasma density is high near the central axis and islow in a portion distant from the central axis. That is, a non-uniformplasma density distribution is formed in the radiation direction withrespect to the central axis. The plasma processing apparatus 10 furtherincludes an electromagnet 60 in order to obtain a uniform plasma densitydistribution even in a processing in which the above-describednon-uniform electric field intensity distribution is formed, e.g., aprocessing using the second radio frequency waves having a radiofrequency.

As illustrated in FIG. 2, the electromagnet 60 is disposed above theupper electrode 36. The electromagnet 60 forms a magnetic fielddistribution having a horizontal component at a position spaced apartfrom the central axis AX greater than a horizontal component on thecentral axis AX in the inner space 12 s of the chamber body 12. That is,the electromagnet 60 forms, in the inner space 12 s, a magnetic fielddistribution having a horizontal component, the magnitude of whichincreases as the distance from the central axis AX increases in theradiation direction. In a portion in which a magnetic field having ahigh horizontal component is formed, the stay time of electronsincreases. As a result, the density of plasma increases in the portionin which the magnetic field having the high horizontal component isformed. Thus, with the plasma processing apparatus 10, it is possible toobtain a uniform plasma density distribution in the radiation directionwith respect to the central axis AX. Therefore, with the plasmaprocessing apparatus 10, the in-plane uniformity of a processing on theworkpiece W is improved.

In an embodiment, the electromagnet 60 includes a yoke 62 and a coil 64.The yoke 62 is formed of a magnetic material. The yoke 62 includes abase portion 62 a and a plurality of cylindrical portions 62 b. The baseportion 62 a has a substantially disc shape and extends in a directionorthogonal to the central axis AX. Each of the plurality of cylindricalportions 62 b has a cylindrical shape and extends downward from the baseportion 62 a. The plurality of cylindrical portions 62 b are providedcoaxially with the central axis AX. The coil 64 is wound around thecentral axis AX. The coil 64 is provided between two adjacentcylindrical portions 62 b in the radial direction. In addition, theelectromagnet 60 may include one or more coils 64. When a plurality ofcoils 64 are present in the electromagnet 60, the plurality of coils 64are provided coaxially with the central axis AX.

The coil 64 of the electromagnet 60 is connected to a current source 66via a wire 68. When current is applied from the current source 66 to thecoil 64, a magnetic field is formed by the electromagnet 60. Since theelectron confinement effect (the effect of preventing diffusion ofelectrons) in the radiation direction (the radial direction) and theeffect of preventing extinction of electrons (the effect of preventingelectrons from reaching an electrode) are well compatible with eachother in a portion in which the angle of a vector of the magnetic fieldformed by the electromagnet 60 is 45°, the density of plasma increasesin the corresponding portion. Thus, when the radius of the workpiece Wis 150 mm, the electromagnet 60 may be configured such that the distancebetween the portion in which the angle of the vector of the magneticfield is 45° and the central axis AX is 135 mm or more and 185 mm orless. Therefore, in an embodiment, the average value of the innerdiameter and the outer diameter of one coil 64 of the electromagnet 60is equal to or greater than the distance between the central axis AX andthe edge of the workpiece W. When the radius of the workpiece W is 150mm, the average value of the inner diameter and the outer diameter ofone coil 64 of the electromagnet 60 is 150 mm or more and 250 mm orless. In addition, the angle of the vector of the magnetic field is 0°when the magnetic field has only a downward component, and is 90° whenthe magnetic field has only a component in the radiation direction(horizontal component). Thus, when the angle of the vector of themagnetic field is 45°, the magnetic field has both a horizontalcomponent and a vertical component.

When the electromagnet 60 is disposed in the space surrounded by thegrounded conductor covering the upper electrode, the first radiofrequency waves are introduced into the electromagnet 60 and/or a wirethat interconnects the electromagnet 60 and a power supply (currentsource). As a result, the electric field intensity in the inner space 12s of the chamber body 12 varies locally. Thus, the electromagnet 60 isdisposed outside the grounded conductor. However, when the electromagnet60 is disposed in the space above the upper end of the groundedconductor, since the distance in the vertical direction from theelectromagnet 60 to the inner space 12 s increases, it is impossible toefficiently form a magnetic field having a sufficient magnitude in theinner space 12 s unless large current is applied to the coil 64. Inaddition, when the electromagnet 60 is disposed on the lateral side ofthe grounded conductor (outside the grounded conductor in the radiationdirection from the central axis), the portion in which the magneticfield having the high horizontal component is formed, or the portion inwhich the magnetic field, the vector of which has an angle of 45°, isnot formed in the inner space 12 s. In order to efficiently form amagnetic field distribution suitable for obtaining a uniform plasmadensity distribution in the inner space 12 s, the grounded conductor 50provides an external space ES in which the electromagnet 60 is disposed.The external space ES is located closer to the inner space 12 s than theupper end of the grounded conductor 50, is separated upward from theupper electrode 36, and is shielded from the upper electrode 36 by thegrounded conductor 50.

The grounded conductor 50 includes a first portion 51, a second portion52, and a third portion 53. The first portion 51 has a cylindricalshape. A central axis of the first portion 51 substantially coincideswith the central axis AX. The first portion 51 extends upward from thechamber body 12. In an example illustrated in FIG. 2, the first portion51 extends upward from the upper end of the sidewall 12 a of the chamberbody 12. A lower end portion of the first portion 51 is interposedbetween the member 37 and the upper end of the sidewall 12 a.

The second portion 52 is spaced apart upward from the upper electrode36, and extends from the first portion 51 toward the central axis AX.The second portion 52 takes the form of a plate that extends in adirection crossing or orthogonal to the central axis AX. The firstportion 51 and the second portion 52 provide a first space IS1 above theupper electrode 36. The first space IS1 is a portion of the space insidethe grounded conductor 50 (i.e., on the upper electrode 36 side). Thefirst space IS1 provides the distance in the vertical direction betweenthe upper electrode 36 and the grounded conductor 50. Thus, capacitivecoupling between the grounded conductor 50 and the upper electrode 36 isprevented. The distance in the vertical direction between the uppersurface of the upper electrode 36 and the lower surface of the secondportion 52 of the grounded conductor 50 is set to a distance of 60 mm ormore, for example.

The third portion 53 has a cylindrical shape. A central axis of thethird portion 53 substantially coincides with the central axis AX. Thethird portion 53 extends closer to the central axis than the firstportion 51. The third portion 53 extends upward from the second portion52. The third portion 53 provides a second space IS2. The second spaceIS2 is the space inside the second portion 52, and is a portion of thespace inside the grounded conductor 50 (i.e., on the upper electrode 36side). The second space IS2 is continuous with the first space IS1. Inaddition, the power supply conductor 48 extends upward through the firstspace IS1 and the second space IS2.

The external space ES is provided by the grounded conductor 50 at theoutside of the third portion 53, on the second portion 52, and above theinterior space 12 s. The external space ES extends in a circumferentialdirection around the central axis AX at the outside of the third portion53 and on the second portion 52. The electromagnet 60 is disposed in theexternal space ES. In addition, the distance in the vertical directionbetween the lower end of the electromagnet 60 disposed in the externalspace ES and the upper surface of the upper electrode 36 is greater than60 mm, and the distance in the vertical direction between the lower endof the electromagnet 60 and the workpiece W placed on the stage 14 maybe equal to or less than 230 mm.

The distance between the electromagnet 60 disposed in the external spaceES and the inner space 12 s is relatively short. In addition, asdescribed above, the electromagnet 60 forms, in the inner space 12 s, amagnetic field distribution having a low horizontal component near thecentral axis AX and a high horizontal component in a position distantfrom the central axis. Thus, by the electromagnet 60 disposed outsidethe grounded conductor 50, a magnetic field distribution suitable forobtaining a uniform plasma density distribution may be efficientlyformed in the inner space 12 s.

The current source 66 is connected to the coil 64 of the electromagnet60 as described above. The electromagnet 60 and the current source 66are disposed outside the grounded conductor 50. Thus, a filter forpreventing high-frequency waves from being introduced into the currentsource 66 may not be provided between the coil 64 and the current source66.

In an embodiment, the grounded conductor 50 further includes a fourthportion 54, a fifth portion 55, and a sixth portion 56. The fourthportion 54 extends above the second portion 52 from the third portion 53in the radiation direction with respect to the central axis AX. Thefourth portion 54 takes the form of a plate that extends in a directioncrossing or orthogonal to the central axis AX. The fifth portion 55 hasa cylindrical shape. A central axis of the fifth portion 55substantially coincides with the central axis AX. The fifth portion 55is farther away from the central axis than the third portion 53, andextends upward from the fourth portion 54. The sixth portion 56 extendsabove the fourth portion 54 from the fifth portion 55 toward the centralaxis AX. The sixth portion 56 takes the form of a plate that extends ina direction crossing or orthogonal to the central axis AX. In anembodiment, the grounded conductor 50 further includes a lid portion 57that extends from the sixth portion to the vicinity of the power supplyconductor 48.

The fourth portion 54, the fifth portion 55, and the sixth portion 56provide a third space IS3. The third space IS 3 is the space surroundedby the fourth portion 54, the fifth portion 55, and the sixth portion56, and is a portion of the space inside the grounded conductor 50. Thethird space IS3 is continuous with the second space IS2. The powersupply conductor 48 further extends upward through the third space IS3.In addition, in the example illustrated in FIG. 2, the first to sixthportions are configured by three members, but the number of membersconstituting the grounded conductor 50 may be any other number.

Hereinafter, a reference will be made on FIG. 4 together with FIG. 2.FIG. 4 is a plan view illustrating an internal configuration of thegrounded conductor of the plasma processing apparatus illustrated inFIG. 2. FIG. 4 illustrates a state where the fifth portion 55 of thegrounded conductor 50 is broken in a horizontal plane. In an embodiment,the plasma processing apparatus 10 further includes a pipe 71 (firstpipe) as illustrated in FIGS. 2 and 4. The pipe 71 extends upward fromthe upper electrode 36 through the first space IS1 and the second spaceIS2, and passes through the third space IS3 so as to extend laterallyand outwardly with respect to the grounded conductor 50. The pipe 71 isconnected to the chiller unit 42 outside the grounded conductor 50. Thecoolant from the chiller unit 42 is supplied to the flow path 40 p viathe pipe 71. In the third space IS3, the pipe 71 is substantiallyshielded from the upper electrode 36 by the fourth portion 54 of thegrounded conductor 50.

The plasma processing apparatus 10 further includes a pipe 72. The pipe72 extends upward through the first space IS1 and the second space IS2,and passes through the third space IS3 so as to extend laterally andoutwardly with respect to the grounded conductor 50. The pipe 72 isconnected to the chiller unit 42 outside the grounded conductor 50. Thecoolant returns from the flow path 40 p to the chiller unit 42 via thepipe 72. In the third space IS3, the pipe 72 is substantially shieldedfrom the upper electrode 36 by the fourth portion 54 of the groundedconductor 50.

In an embodiment, the plasma processing apparatus 10 further includes apipe 73 (second pipe). The pipe 73 extends upward from the upperelectrode 36 through the first space IS1 and the second space IS2, andpasses through the third space IS3 so as to extend laterally andoutwardly with respect to the grounded conductor 50. The pipe 73 isconnected to the gas supply unit 41 outside the grounded conductor 50.The gas output from the gas supply unit 41 is supplied to the upperelectrode 36, i.e., the shower head via the pipe 73. In the third spaceIS3, the pipe 73 is substantially shielded from the upper electrode 36by the fourth portion 54 of the grounded conductor 50. In addition, thegas supply unit 41 and the upper electrode 36 (i.e., the shower head)may be connected to each other via a plurality of pipes.

In an embodiment, the plasma processing apparatus 10 further includes aDC power supply 74 and a wire 75. The DC power supply 74 is configuredto generate a negative DC voltage to be applied to the upper electrode36. The wire 75 connects the DC power supply 74 and the upper electrode36 to each other. The wire 75 may include a coil 75 c. The coil 75 c isprovided in the third space IS3. The wire 75 extends upward from theupper electrode 36 through the first space IS1 and the second space IS,and passes through the third space IS3 so as to extend laterally andoutwardly with respect to the grounded conductor 50. The wire 75 iselectrically insulated from the fifth portion 55 and the groundedconductor 50. The wire 75 is connected to the DC power supply 74 outsidethe grounded conductor 50. In the third space IS3, the wire 75 issubstantially shielded from the upper electrode 36 by the fourth portion54 of the grounded conductor 50.

In an embodiment, the plasma processing apparatus 10 further includes acontroller 80. The controller 80 is configured to control each part ofthe plasma processing apparatus 10. The controller 80 may be a computerdevice. The controller 80 may include a processor, a storage device suchas a memory, an input device such as a keyboard, a mouse or a touchpanel, a display device, and an input/output interface of a controlsignal, for example. The storage device stores a control program andrecipe data. The processor of the controller 80 executes the controlprogram and sends a control signal for controlling each part of theplasma processing apparatus 10 according to the recipe data. Thecontroller 80 may control each part of the plasma processing apparatus10 in order to execute the method MT.

Hereinafter, a reference will be made on FIG. 5. FIG. 5 is a graphillustrating a calculation result of a magnetic field distribution thatmay be formed by the plasma processing apparatus illustrated in FIG. 2.In FIG. 5, the horizontal axis indicates the distance from the centralaxis AX, and the vertical axis indicates the magnetic flux density. FIG.5 illustrates a magnetic flux density distribution indicating thedistribution of a magnetic field BA, a magnetic flux densitydistribution indicating the distribution of a horizontal component BH ofthe magnetic field BA, and a magnetic flux density distributionindicating the distribution of a vertical component BV of the magneticfield BA. The distributions of the magnetic field and two componentsthereof illustrated in FIG. 5 are the distributions in the plane spacedapart downward from the lower end portion of the electromagnet 60 by 174mm, i.e., the distributions in the upper surface of the stage 14.Conditions for calculating the distributions of the magnetic field andtwo components thereof illustrated in FIG. 5 are as follows.

<Calculation Conditions>

Inner diameter (radius) of the coil 64: 132 mm

Outer diameter (radius) of the coil 64: 173 mm

Number of turns of the coil 64: 215 turns

Current supplied to the coil 64: 4 [A]

Distance between the lower end of the electromagnet 60 and the workpieceW placed on the stage 14: 174 mm

As can be seen from the calculation result of the magnetic fielddistribution illustrated in FIG. 5, according to the electromagnet 60,it is possible to form a magnetic field distribution having a horizontalcomponent in a portion spaced apart from the central axis AX greaterthan a horizontal component on the central axis AX.

Hereinafter, a reference will be made on FIG. 6. FIG. 6 is a graphillustrating a measurement result of an ion flux distribution in theinner space of the plasma processing apparatus illustrated in FIG. 2. Inan experiment for obtaining the measurement result illustrated in FIG.6, a magnetic field was formed in the inner space 12 s by theelectromagnet 60 by generating plasma in the inner space 12 s in a statewhere a disk-shaped sample is placed on the stage 14. Then, the rate ofincrease per unit time (dT/dt) of the temperature of the sample wasobtained at a plurality of measurement points on the diameter of thesample. In addition, the rate of increase (dT/dt) is a parameter thatreflects the amount of ion flux. In the experiment, an ion fluxdistribution was measured by setting the current supplied to the coil 64of the electromagnet 60 to 0 [A], 1 [A], 4 [A], and 6.5 [A]. Otherconditions of the experiment are described below.

<Conditions of Experiment>

Pressure of the inner space 12 s: 20 mTorr (2.67 Pa)

Gas supplied to the inner space 12 s: Ar gas at 1000 sccm

First radio frequency waves: 60 MHz, 100 W

Second radio frequency waves: 40 MHz, 100 W

In FIG. 6, the horizontal axis indicates the position of each of theplurality of measurement points and the distance from the central axisAX. The measurement point specified by a positive distance is on oneside with respect to the central axis AX on the above-described diameterand the measurement point specified by a negative distance is on theother side with respect to the central axis AX on the above-describeddiameter. In FIG. 6, the vertical axis indicates the rate of increase(dT/dt). As illustrated in FIG. 6, when the current supplied to the coil64 of the electromagnet 60 is 0 [A], the rate of increase (dT/dt), i.e.,the ion flux was reduced with increasing distance from the central axisAX. That is, when the current supplied to the coil 64 is 0 [A], anon-uniform plasma density distribution was formed. When the currentsupplied to the coil 64 increases, the difference in ion flux betweenthe plurality of measurement points was reduced. That is, it wasconfirmed that a uniform plasma density distribution may be formed byforming a magnetic field in the inner space 12 s by the electromagnet60.

Referring again to FIG. 1, the method MT will be described by taking acase where the plasma processing apparatus 10 is used as an example. Themethod MT is executed in a state where the workpiece W is accommodatedin the inner space 12 s of the chamber main body 12. As illustrated inFIG. 1, the method MT includes steps ST1 and ST2.

In step ST1, a first plasma processing is executed on the workpiece W.In step ST1, the workpiece W is processed by plasma of a first gassupplied to the inner space 12 s. In step ST1, second radio frequencywaves may be supplied or may not be supplied to the lower electrode 18.When the second radio frequency waves are supplied to the lowerelectrode 18 in step ST1, power of the second radio frequency waves setin step ST1 is less than power of the second radio frequency wavessupplied to the lower electrode 18 in step ST2.

In step ST2, a second plasma processing is performed on the workpiece W.In step ST2, the workpiece W is processed by plasma of a second gassupplied to the inner space 12 s. In step ST2, the second radiofrequency waves are supplied to the lower electrode 18. In step ST2,power of the second radio frequency waves is set to be greater thanpower of the second radio frequency waves in step ST1. In an embodiment,a frequency of the second radio frequency waves is greater than 13.56MHz. The frequency of the second radio frequency waves may be equal toor greater than 40 MHz, and may be equal to or greater than 60 MHz.

In step ST2, a magnetic field distribution having a horizontal componenton the edge side of the workpiece W greater than a horizontal componenton the center of the workpiece W is formed in the inner space 12 s bythe electromagnet 60.

Step ST1 and step ST2 may be alternately repeated. When step ST1 andstep ST2 are alternately repeated, it is determined in step ST3 whetheror not a stop condition is satisfied. The stop condition is determinedto be satisfied, for example, when the number of times a sequenceincluding step ST1 and step ST2 is executed has reached a predeterminednumber of times. When it is determined in step ST3 that the stopcondition is not satisfied, step ST1 is executed again, andsubsequently, step ST2 is executed. On the other hand, when it isdetermined in step ST3 that the stop condition is satisfied, theexecution of the method MT ends.

In step ST2 of the method MT, the power of the second radio frequencywaves is set to be higher than the power of the second radio frequencywaves set in step ST1. Thus, while the second plasma processing in stepST2 is executed, the electric field intensity on the center of theworkpiece W increases, and the electric field intensity on the edge sideof the workpiece W decreases. That is, while the second plasmaprocessing is executed, a non-uniform electric field intensitydistribution is formed in the radiation direction with respect to thecentral axis AX. While the second plasma processing is executed, theabove-described magnetic field distribution is formed in the inner space12 s. In a portion in which a magnetic field having a high horizontalcomponent is formed, the stay time of electrons increases. As a result,the density of plasma increases in the portion in which the magneticfield having the high horizontal component is formed. Therefore, auniform plasma density distribution is made during the execution of thesecond plasma processing. Moreover, since a uniform plasma densitydistribution is made by the magnetic field distribution formed by theelectromagnet 60, a uniform plasma density distribution may be made at ahigh speed at a point in time at which a plasma processing to beexecuted is switched from the first plasma processing to the secondplasma processing. When step ST1 and step ST2 are alternately repeated,it is particularly advantageous to use the electromagnet 60 capable ofmaking a uniform plasma density distribution at a high speed.

In an embodiment, the first gas includes a fluorocarbon gas, forexample, C₄F₈ gas. The second gas includes a rare gas such as He gas, Negas, Ar gas, Kr gas, or Xe gas. The method MT of the embodiment mayselectively etch a first region formed of silicon oxide with respect toa second region formed of silicon nitride.

FIG. 7 is a partially enlarged cross-sectional view of an workpiece towhich an embodiment of the method illustrated in FIG. 1 is applicable.The workpiece W illustrated in FIG. 7 includes an underlying region UR,a plurality of protruding regions PR, a first region R1, a second regionR2, and a mask MK. The workpiece W may be, for example, a productobtained during the manufacture of a fin field effect transistor.

The underlying region UR may be formed of polycrystalline silicon, forexample. In an example, the underlying region UR is a fin region and hasa substantially rectangular parallelepiped shape. The plurality ofprotruding regions PR are provided on the underlying region UR, and arearranged substantially in parallel to each other. These protrudingregions PR may be, for example, gate regions. The second region R2 isformed of silicon nitride. The second region R2 is provided so as tocover the protruding regions PR and the underlying region UR. The secondregion R2 provides a recess between two adjacent protruding regions PR.The first region R1 is formed of silicon oxide. The first region R1 isprovided in the above-described recess that may be provided by thesecond region R2. In addition, the first region R1 is provided so as tocover the second region R2. The mask MK is provided on the first regionR1. The mask MK is patterned so as to provide an opening above therecess provided by the second region R2. The width of the opening in themask MK is greater than the width of the recess provided by the secondregion R2. The mask MK is a mask formed of an organic film. The mask MKmay be formed by a photolithography technique.

Hereinafter, the method MT of an embodiment will be described by takinga case of being applied to the workpiece W illustrated in FIG. 7 as anexample. However, the method MT of the embodiment may be applied to anyother workpiece including a first region formed of silicon oxide and asecond region formed of silicon nitride. Hereinafter, a reference willbe made on FIGS. 8, 9A, 9B and 10, in addition to FIGS. 1 and 7. FIG. 8is a partially enlarged cross-sectional view of the workpiece processedfrom a state illustrated in FIG. 7. FIG. 9A is a partially enlargedcross-sectional view of the workpiece in a state after execution of stepST1 in the embodiment of the method illustrated in FIG. 1, and FIG. 9Bis a partially enlarged cross-sectional view of the workpiece in a stateafter execution of step ST2 in the embodiment of the method illustratedin FIG. 1. FIG. 10 is a partially enlarged cross-sectional view of theworkpiece after the embodiment of the method illustrated in FIG. 1 isapplied.

In the method MT of the embodiment, the first region R1 may be etchedonly by step ST1 and step ST2. Alternatively, the first region R1 may beetched by another plasma etching processing before step ST1 is initiallyexecuted, until the second region R2 is exposed (see FIG. 8), or justbefore the second region R2 is exposed. For example, the first region R1may be etched by active species such as ions and/or radicals from plasmaof a fluorocarbon gas until the second region R2 is exposed (see FIG.8), or just before the second region R2 is exposed.

In step ST1 of the method MT of the embodiment, the workpiece W isprocessed with plasma of the above-described first gas including afluorocarbon gas. In addition to the fluorocarbon gas, the first gas mayinclude a rare gas such as oxygen gas and Ar gas. In step ST1, a depositfilm DP containing fluorocarbon is formed on the workpiece W. In stepST1, the film DP is formed so that the film thickness of the film DP onthe second region R2 is greater than the film thickness of the film DPon the first region R1.

Specifically, in step ST1, the first gas is supplied to the inner space12 s, and the pressure in the inner space 12 s is reduced to adesignated pressure by the exhaust device 34. By supplying the firstradio frequency waves, the first gas is excited in the inner space 12 s.As a result, plasma of the first gas is generated in the inner space 12s. In step ST1, the power of the second radio frequency waves is set tobe less than the power of the second radio frequency waves in step ST2.In step ST1, the second radio frequency waves may not be supplied to thelower electrode 18.

In step ST1, the temperature of the workpiece W is set to 20° C. orhigher and 250° C. or lower. The temperature of the workpiece W isadjusted by the heat exchange medium supplied to the flow path 18 p andthe above-described one or more heaters provided in the electrostaticchuck 20. When the temperature of the workpiece W is set to such atemperature, as illustrated in FIG. 9A, the deposit film DP containingfluorocarbon is formed on the workpiece W. As illustrated in FIG. 9A,the film thickness of the film DP is large on the second region R2 andis small on the first region R1. In addition, the temperature exceeding250° C. is the glass transition temperature of the mask MK, and at thistemperature, the difference between the film thickness of the film DPformed on the first region R1 and the film thickness of the film DPformed on the second region R2 is reduced. In addition, even at atemperature lower than 20° C., the difference between the film thicknessof the film DP formed on the first region R1 and the film thickness ofthe film DP formed on the second region R2 is reduced.

In step ST2, the workpiece W processed in step ST1 is processed byplasma of the above-described second gas including a rare gas. Thesecond gas may be a gas including only the rare gas. Alternatively, thesecond gas may include oxygen gas, in addition to the rare gas. In stepST2, the second gas is supplied to the inner space 12 s, and thepressure in the inner space 12 s is reduced to a designated pressure bythe exhaust device 34. By supplying the second radio frequency waves,the second gas is excited in the inner space 12 s. As a result, plasmaof the second gas is generated in the inner space 12 s. In step ST2, thesecond radio frequency waves are supplied to the lower electrode 18. Instep ST2, the power of the second radio frequency waves is set to begreater than the power of the second radio frequency waves in step ST1.

In step ST2, the workpiece W is irradiated with ions of the rare gas.When the film DP is irradiated with the ions of the rare gas, the firstregion R1 is etched by radicals of fluorocarbon contained in the filmDP. On the other hand, the film DP on the second region R2 decreases,but protects the second region R2 so as to prevent etching of the secondregion R2. When step ST2 is executed, the workpiece W illustrated inFIG. 9A becomes a state illustrated in FIG. 9B. Then, by alternatelyrepeating steps ST1 and ST2, as illustrated in FIG. 10, the first regionR1 in the recess provided by the second region R2 is removed, so that anopening HL is formed. That is, the opening HL is formed in aself-aligning manner.

Incidentally, when the width of the recess provided by the second regionR2 is small, by execution of step ST1, a thick deposit film is formed onthe first region R1 that is present in the narrow recess. When the thickdeposit film is formed on the first region R1, the etching of the firstregion R1 does not proceed in step ST2. Thus, when the width of therecess provided by the second region R2 is narrow, it is necessary toreduce the film thickness of the deposit film DP formed on the workpieceW. When the film thickness of the deposit film DP is small, in order toprevent etching of the second region R2, it is necessary to lower theenergy of ions of the rare gas with which the workpiece W is irradiated.The energy of the ions is lowered by using the second radio frequencywaves having a radio frequency. For example, the second radio frequencywaves having a frequency greater than 13.56 MHz, a frequency of 40 MHzor higher, or a frequency of 60 MHz or higher are used. When the secondradio frequency waves having a radio frequency are used, thenon-uniformity of the electric field intensity distribution formed instep ST2 becomes more conspicuous. Such non-uniformity is eliminated orsuppressed by forming the above-described magnetic field by theelectromagnet 60 in step ST2.

While various embodiments have been described above, variousmodifications may be made without being limited to the above-describedembodiments. The method MT may be executed using a plasma processingapparatus other than the plasma processing apparatus 10, i.e., anarbitrary plasma processing apparatus that is capable of supplyingsecond radio frequency waves (bias radio frequency waves) to the lowerelectrode and that is capable of forming the same magnetic fielddistribution as the magnetic field distribution formed by theelectromagnet 60 in the inner space of the chamber body. As such aplasma processing apparatus, a capacitively coupled plasma processingapparatus configured to supply first radio frequency waves to a lowerelectrode, an inductively coupled plasma processing apparatus, or aplasma processing apparatus configured to excite a gas by surface wavessuch as microwaves is illustrated.

In addition, the electromagnet of the plasma processing apparatus usedin the method MT may include one or more coils.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A plasma processing method for a workpiece in aplasma processing apparatus, the plasma processing apparatus including:a chamber body configured to provide an inner space; a stage configuredto provide a placing region for the workpiece, and provided in the innerspace, the center of the placing region being located on a central axisof the chamber body; a lower electrode provided in the stage; a gassupply unit configured to supply a first gas and a second gas to theinner space of the chamber body; a first radio frequency power supplyconfigured to supply first radio frequency waves; a second radiofrequency power supply electrically connected to the lower electrode andconfigured to supply second radio frequency waves having a frequencylower than a frequency of the first radio frequency waves; and anelectromagnet configured to form a magnetic field in the inner space ofthe chamber body, the plasma processing method comprising: providing theworkpiece in the inner space of the chamber body; performing a firstplasma processing on the workpiece by plasma generated from a first gassupplied to the inner space; and performing a second plasma processingon the workpiece by plasma generated from a second gas supplied to theinner space, wherein power of the second radio frequency waves set inthe second plasma processing is greater than power of the second radiofrequency waves set in the first plasma processing, and in the secondplasma processing, a magnetic field distribution having a horizontalcomponent on an edge side of the workpiece that is greater than ahorizontal component on a center of the workpiece is formed by theelectromagnet.
 2. The plasma processing method of claim 1, furthercomprising alternately repeating the first plasma processing and thesecond plasma processing.
 3. The plasma processing method of claim 1,wherein the workpiece includes a first region formed of silicon oxideand a second region formed of silicon nitride, the first gas includes afluorocarbon gas, the first plasma processing forms a deposit filmcontaining fluorocarbon on the workpiece, the second gas includes a raregas, and the second plasma processing irradiates the workpiece havingthe deposit film with ions of the rare gas to etch the first region. 4.The plasma processing method of claim 3, wherein a recess formed by thesecond region includes the first region.
 5. The plasma processing methodof claim 1, wherein the frequency of the second radio frequency waves isgreater than 13.56 MHz.
 6. The plasma processing method of claim 5,wherein the frequency of the second radio frequency waves is equal to orgreater than 40 MHz.
 7. The plasma processing method of claim 5, whereinthe frequency of the second radio frequency waves is equal to or greaterthan 60 MHz.